In the field of the preservation of foodstuffs and drinks in particular, the deleterious effects of oxygen present in aqueous solution are well known. In this instance, these effects result in changes in color and changes in taste. These effects are due mainly to the free radicals formed during the reaction of oxygen with reducing solutes. In order to reduce these deleterious effects of oxygen, antioxidant agents are used.
Various systems which are used for removing oxygen from foodstuffs or drinks are known, such as, for example, catalase and oxidoreductases which are used for protecting foodstuffs against degradation effects due to oxygen. This system significantly reduces the concentration of dissolved oxygen, but it unfortunately has no effect on oxygen present in free-radical form. Free-radical oxygen is responsible for degradation mechanisms.
Systems which employ superoxide dismutase alone are known. In particular, reference is made to U.S. Pat. No. 3,920,521, which is hereby incorporated by reference in its entirety. However, superoxide dismutase does not actually consume oxygen, and it does not prevent all reactions with the different reducing agents in the medium. According to reaction (1), superoxide dismutase traps the superoxide ion and reforms oxygen. EQU (1) O.sub.2..sup.31 +O.sub.2..sup.31 +2H.sup.30 .fwdarw.H.sub.2 O.sub.2 +O.sub.2
Moreover, it is well known that superoxide dismutase has only a weak antioxidant power at a pH below 5, and this is due to the transitory existence of the O.sub.2..sup.31 radical at acid pH, as shown in equations (2) and (3). EQU (2) O.sub.2..sup.31 +H.sup.30 .fwdarw.HO.sub.2.(pk=4.88) EQU (3) H.sup.30 +O.sub.2..sup.31 .fwdarw.HO.sub.2..sup.30 +O.sub.2 (K=2.5.times.10.sup.8)
At the present time, for the preservation of foodstuffs and especially drinks, either the molecular oxygen is quenched, or an antioxidant is added which will have the effect of maintaining the oxygen content at a certain prescribed content.
In fact, to achieve a considerable improvement in the preservation factor, it appears to be necessary to trap both molecular oxygen and free-radical oxygen, so as to avoid all risk of oxidative degradation of the medium.